Humans 'may have saved world from ice age'

HUMANS may have unwittingly saved themselves from a looming ice age by interfering with the Earth's climate, according to a new study.

The findings from a team of American climate experts suggest that were it not for greenhouse gases produced by humans, the world would be well on the way to a frozen Armageddon.

Scientists have traditionally viewed the relative stability of the Earth's climate since the end of the last ice age 10,000 years ago as being due to natural causes, but there is evidence that changes in solar radiation and greenhouse gas concentrations should have driven the Earth towards glacial conditions over the last few thousand years.

What stopped it has been the activity of humans, both ancient and modern, argue the scientists.

Over the last 8,000 years carbon dioxide levels in the atmosphere have gradually risen, when previous trends indicated that it should have dropped.

Methane, another greenhouse gas, had also increased instead of fallen.

The unexpected trends could be explained by massive early deforestation in Eurasia, rice farming in Asia, the introduction of livestock, and the burning of wood and plant material, all of which led to an outpouring of greenhouse emissions.

The United States researchers, led by William Ruddiman from the University of Virginia in Charlottesville, used a climate model to test what would happen if these greenhouse gases were reduced to their "natural" level.

They wrote in the journal, Quaternary Science Reviews: "In the absence of anthropogenic contributions, global climate is almost 2C cooler than today and roughly one-third of the way toward full glacial temperatures."

At the peak of the last ice age, which began 70,000 years ago, 97% of Canada was covered by ice.

The research showed that without the human contribution to global warming, Baffin Island would today be in a condition of "incipient glaciation".

"Portions of Labrador and Hudson Bay would also have moved very close to such a state had greenhouse gas concentrations followed natural trends," said the scientists.

The experiment had probably underestimated the amount of ice that would exist today in north-east Canada without human interference, they said.

Anthropologist Dr Benny Peiser, from Liverpool John Moores University, said: "If the research findings are correct, a radical change in the perception of anthropogenic greenhouse gas emissions will be required.

"Instead of driving us to the brink of environmental disaster, human intervention and technology progress will be seen as vital activities that have unintentionally delayed the onset of a catastrophic ice age."